GB2348686A

GB2348686A - Pipe coupling with grip rings

Info

Publication number: GB2348686A
Application number: GB9907410A
Authority: GB
Inventors: Steven Dudley
Original assignee: Marley Extrusions Ltd
Current assignee: DHM Plastics Ltd
Priority date: 1999-03-31
Filing date: 1999-03-31
Publication date: 2000-10-11
Anticipated expiration: 2019-03-31
Also published as: GB2348686B; GB9907410D0

Abstract

A pipe coupling 1 has a body 2 defining a bore 3 to receive a pipe (25, figure 4), a seal 8 and a pair of identical, interlocked grip rings 5, 6 to engage the pipe. The grip rings are of plastics with embedded metal teeth 15, and are movable axially. The end of the coupling is provided with a cam surface 17 which engages the leading grip ring 5 as the rings move axially, so that both grip rings are compressed radially to grip the pipe. The leading grip ring 5 is also provided with a surface 19 which can be engaged by an axially movable release tool (24, figure 4 and 5) so as to disengage both grip rings from the pipe. The two grip rings are interlocked by means of the leading ring 5 having a recess (20, figure 3) which receives part of the trailing ring 6 so as to transmit axial and radial forces in both directions.

Description

Pipe Couplings with Grip Rings This invention relates to pipe couplings incorporating grip rings, of the type used for example to join together water supply pipes in plumbing systems.

Such pipe couplings typically comprise a body into which a pipe is inserted, a seal such as an 0-ring for sealing around the pipe once inserted, and a grip ring for resisting removal of the pipe. In one arrangement, the grip ring is movable and in use is urged axially against means which compress the ring and cause it to grip the pipe. One such system is disclosed in PCT Application PCT/GB96/01611. In that system, the preferred grip ring consists of a moulded plastics body in which are embedded projecting metal teeth for engaging the surface of the pipe.

In such arrangement, the amount of grip provided by the ring is a function of, amongst other things, the peripheral extent of metal available to grip the pipe.

In developing the present invention, it has become apparent that in some circumstances the amount of grip required exceeds that possible with a single ring of metal teeth, for example when designing a coupling to work with higher pressures or larger diameter pipes.

In EP-A-0 735 306 there is disclosed in one embodiment a grip ring which is made entirely of polymeric material. This has three coaxial gripping portions. The grip ring is used in a coupling for composite pipe which is coated externally with plastics.

In a modification of this embodiment, a single metal ring with a plurality of teeth is moulded into the polymeric grip ring so that it can be used with both standard copper and plastic pipe. However, neither of these arrangements would provide the level of grip necessary in certain circumstances.

It might be considered desirable to mould a plurality of coaxial metal rings into a plastic body so as to increase the extent of metal available for gripping a pipe. However, that presents manufacturing problems. It is difficult to mould two rings of metal teeth into a plastic body, because of the natural undercuts created between the two rows of teeth.

According to one aspect of the present invention there is provided a pipe coupling comprising a body defining a pipe receiving bore, a seal within the bore, and a grip ring within the bore, the grip ring being movable axially into engagement with a cooperating surface which compresses the grip ring radially into engagement with a pipe in the bore in use, characterised in that a second, separate grip ring is provided in the bore, the second grip ring being engaged in use with the first grip ring in such a way that engagement of the first grip ring with the cooperating surface also urges the second grip ring into engagement with a pipe in the bore in use.

In the preferred arrangement the first and second grip rings comprise a plastics body in which are embedded metallic pipe gripping portions. The provision of separately manufactured first and second grip rings means that an additional extent of metallic pipe gripping portions can be provided without the need to mould two sets of metallic portions into the same plastics body. Although the grip rings are separate items within the coupling they cooperate mechanically to achieve the desired effect. Preferably the first and second grip rings are identical, to reduce manufacturing costs and to ensure that there will be no errors in assembling the components in the correct order.

Preferably, the trailing edge of the first grip ring and the leading edge of the second grip ring cooperate so that as the first grip ring is urged into engagement with a pipe, so is the second grip ring. For the purposes of this specification the"leading edge"is that facing the opening of the coupling through which a pipe will be passed into the coupling. In the preferred embodiment, the trailing edge of the first grip ring is tapered and overlies a correspondingly tapered surface on the leading edge of the second grip ring. Where the first and second grip rings are identical, the profile of the leading and trailing edges is such that the leading edge of a ring can engage the cooperating surface of the coupling when used as the first ring, and the profiled trailing edge of a like ring when used as the second ring.

In a preferred arrangement the two grip rings interlock. Thus, in one embodiment the trailing edge of the first grip ring is formed as a"V"-shaped groove, and the leading edge of the second grip ring is formed as a corresponding"V"-shaped projection which engages in the groove.

The grip rings of the present invention are of particular use in couplings of the type disclosed in PCT Application PCT/GB96/01611 or EP-A-0897082 in which a release tool may be moved axially with respect to a pipe to release the gripping means from the pipe. The release tool has a surface which engages a camming surface on the grip ring. Accordingly, viewed from another aspect the present invention provides a pipe coupling comprising a main body defining a pipe receiving bore, an end member which is attached to one end of the main body and part of which defines a mouth for the bore, a seal within the bore, and an axially movable grip ring within the bore between the seal and the mouth, the grip ring including pipe-engaging portions which engage the surface of a pipe received in the bore in use; wherein the end member is provided with a first cam surface and the grip ring is provided on its leading edge with a second cam surface for engagement with the first cam surface, such that engagement of the first and second cam surfaces causes the engaging portions of the grip ring to be urged into gripping engagement with the surface of a pipe received in the bore in use; and wherein the grip ring is further provided on its leading edge with a third cam surface which is arranged so that it can be engaged by a release tool which is movable axially with respect to a pipe in use so that the engaging portions of the grip ring can be urged away from engagement with the pipe; characterised in that a second, like grip ring is provided within the bore, the second grip ring having cam surfaces on its leading edge corresponding to the second and third cam surfaces of the first grip ring, and in that the trailing edge of the first grip ring is provided with a recess which receives the leading edge of the second grip ring, including the cam surfaces thereon. The release tool may be integral with the coupling or a separate item as disclosed in PCT Application PCT/GB96/01611.

Viewed from another aspect of the invention there is provided a grip ring for use in a pipe coupling, the grip ring having pipe gripping portions and having a leading edge and a trailing edge, the leading edge being provided with a radially outwardly facing, tapering cam surface for engaging a member in the coupling which will cause the grip ring to grip a pipe in use, and a radially inwardly facing, tapering cam surface for engaging a release tool which will cause the grip ring to release its grip on a pipe in use, characterised in that the trailing edge of the grip ring is profiled so as to be capable of receiving the leading edge of a like grip ring.

The engagement of the first and second grip rings may be such as to permit relative rotation about the axis of the bore of the coupling. The two grip rings may engage each other directly or through an intermediate member which does not serve as a grip ring or at least not in the same manner. More than two grip rings may be provided, the arrangement being such that each grip ring transmits forces to the next so that they are all urged into engagement with a pipe in use. Thus, any number of identical, interlocking rings may be used as necessary in a particular application. In some applications a single one of these grip rings may be employed, making it unnecessary to manufacture a special grip ring for such a purpose.

When the present invention is used in the context of a system which uses a release tool, it is desirable if the cooperation between the two (or more) grip rings is such that the release effect is transmitted from the first grip ring, which will be engaged by the release tool, to the other grip ring (s). Thus, the release tool may have a cam surface to engage a corresponding cam surface on the leading edge of a first grip ring to urge the gripping portions radially outwardly and away from gripping engagement with a pipe. The second grip ring will have a similar cam surface on its leading edge, and to cooperate with this there is provided a further cam surface on the trailing edge of the first grip ring. As the gripping portions of the first grip ring are moved radially out of engagement with a pipe under the action of the release tool which is moved axially, so the movement is transmitted to the second grip ring.

Thus, in certain preferred embodiments of the present invention the cooperation between two grip rings may be such that axial, radial outwards and radial inwards forces are transmitted between the two grip rings.

A grip ring which is constructed so that it can be used in an interlocking fashion with other grip rings is advantageous in its own right and viewed from another aspect of the invention there is provided a grip ring for use in a pipe coupling, the grip ring comprising a plastics body in which are embedded metallic pipe gripping portions, characterised in that the plastics body is provided at its trailing edge with means for interlocking engagement with the leading edge of a like grip ring when arranged coaxially therewith.

Preferably, this is achieved by forming the trailing edge of the grip ring as a groove adapted to receive the leading edge of a like grip ring.

As regards the basic construction of the grip ring and provision of the metallic pipe gripping portions, this may be achieved in any desired manner such as described for example in PCT/GB96/01611. The grip ring is preferably in the form of a plastics split ring. The metallic portions may be in the form of teeth provided by a split metal ring embedded in the plastics split ring. The basic construction of the coupling may be as described in PCT/GB96/01611 or as in EP-A-0897082.

The use of a plurality of interlocking grip rings may be of use in other types of couplings, such as those which employ an essentially static grip ring which is not moved against a cooperating surface in order to be urged into engagement with a pipe but is inherently adapted to grip the pipe with sufficient force once the pipe has been pushed through the ring.

Accordingly, viewed from another aspect the present invention provides a pipe coupling comprising a body defining a pipe receiving bore, a seal within the bore, and a grip ring within the bore, characterised in that a second grip ring is provided within the bore in an interlocked arrangement with the first grip ring.

Preferably the two grip rings are identical. If desired a coupling could be provided with three, four or more interlocked grip rings. Preferably the grip rings are interlocked by means of the leading edge of one ring engaging in a groove formed in the trailing edge of the other ring.

There may be other types of grip ring which could be interlocked to provide increased grip within a coupling, and the two or more grip rings need not be identical. Thus viewed from a still further aspect there is provided a pipe coupling comprising pipe gripping means which includes at least two coaxially arranged grip rings which have been manufactured separately but have been mechanically interlocked during assembly of the coupling.

The use of two grip rings, each comprising a plastics body in which are embedded metallic pipe gripping portions, is advantageous in terms of increasing the amount of metal available for gripping whilst avoiding the need to mould two sets of metallic portions into the same plastics body. Whilst these are preferably used as separate items which are mechanically engaged in the coupling, it would be possible to manufacture them separately and then to bond them together by means of welding, adhesive or other suitable means even though that increases the complexity and cost of manufacture. Thus viewed from a further aspect of the invention there is provided a pipe coupling comprising pipe gripping means which includes at least two coaxially arranged grip rings which have been manufactured separately but have been joined together, characterised in that each grip ring comprises a plastics body in which are embedded metallic pipe gripping portions.

An embodiment of the invention will now be described by way of example and with reference to the accompanying drawings in which : Figure 1 is an exploded diagrammatic view of a pipe coupling in accordance with the present invention, incorporating a pair of interlocking grip rings; Figure 2 is a diagrammatic view of the coupling of Figure 1 in the assembled state; Figure 3 is a cross section through the pair of grip rings; Figure 4 is an external view of an alternative pipe coupling in accordance with the invention, together with a cross section through a release tool used to release the grip rings from a pipe in use; and Figure 5 is an end view of the release tool.

Turning now in detail to the drawings, the pipe coupling 1 of Figures 1 and 2 is in the form of a right angle elbow coupling. In this case only one end is provided with the coupling arrangement of the present invention, but of course both ends could be so provided and the invention is not restricted to elbow junctions or any other particular format. The coupling 1 comprises a plastics body 2 defining a bore 3 for receiving a pipe (not shown) such as a copper pipe for plumbing purposes.

Into this bore 3 are fitted in a coaxial fashion, in order from the outside, an end member 4, a pair of grip rings 5 and 6, a washer 7 and a seal 8 in the form of an 0-ring. The seal 8 abuts against a shoulder 9 in the bore 3 where the internal diameter of the bore is reduced to a size which is slightly greater than the external diameter of a copper or other pipe (not shown) with which the coupling is to be used.

The assembly is held together by means of a sleeve 10 of stainless steel or another suitable metal which holds the end member 4 in place. The sleeve 10 fits over the plastics body 2. The body 2 is formed with a ridge 11 and the sleeve 10 has an outwardly directed extension 12 which receives this ridge in the manner described in EP-A-0897082.

The present embodiment of the invention concerns the use of the pair of grip rings 5 and 6 as opposed to a single grip ring as in the prior art. The basic construction of each grip ring, as shown in Figures 1 and 3, is similar to that of the grip ring used in some embodiments of PCT Application PCT/GB96/01611. The grip rings are identical and only ring 5 will be described in detail by way of example. Grip ring 5 is in the form of a resilient split ring comprising a plastics body 13 divided into segments by grooves 14, in which is embedded a steel ring 15 which is also split into segments, forming teeth 16 which project from the body 13. These teeth 16 are used to grip the surface of a pipe when inserted into the coupling. The grip rings 5 and 6 are manufactured with diameters which are slightly less than the diameter of the pipe and thus naturally grip the pipe under their own resilience.

The end member 4 is provided with an inwardly directed, tapering first cam surface 17 and the leading edge 18 of the first grip ring 5 is formed with a cooperating radially outwardly directed, tapering second cam surface 18. When a pipe is inserted into the coupling and through the grip rings and seal, and the system is placed under pressure, the grip ring 5 is urged axially towards the end member 4. The first and second cam surfaces 17 and 18 cooperate to compress the grip ring 5 and urge the teeth 16 into contact with the pipe. The Leading edge of the first grip ring 6 is also provided with a radially inwardly directed tapering third cam surface 19. As will be described in more detail below, a release tool can be engaged with this to release the grip ring 5 from a pipe. In this regard the grip ring 5 operates in the same way as the grip rings in PCT Application PCT/GB96/01611 or EP-A-0897082.

As shown most clearly in Figure 3, the grip ring 5 is formed at its trailing edge with a groove 20 whose profile matches that of the leading edge of the grip ring. In this manner, the groove 20 may receive the leading edge 21 of the second grip ring 6, which in this embodiment is identical to the first grip ring, so that the two grip rings are interlocked. The manner of engagement permits a degree of relative rotation between the two grip rings which may be beneficial when a pipe is being inserted into or removed from the coupling.

In use, when a pipe is inserted and the system is placed under pressure, axial force is transmitted via the seal 8 and the washer 7 to the second grip ring 6.

This in turn transmits axial force to the first grip ring 5 whose second cam surface 18 cooperates with the first cam surface 17 of the end member 4 to urge the first grip ring to close up and grip the pipe. This force is in turn transmitted to the second grip ring 6 which is also closed up so that its teeth 22 grip the pipe in the same manner.

When a release tool is inserted into the coupling in the manner described below, there is a rearwards axial force on the first grip ring 5, accompanied by a radially outwards force under the action of the release tool on the third cam surface 19, provided on the first grip ring 5. This is transmitted as both an axial and a radially force to the second grip ring 6 by virtue of the inner portion of the groove 20 at the trailing edge of the ring 5 engaging the inwardly facing cam surface at the leading edge of the grip ring 6.

Figure 4 shows the exterior of an alternative pipe coupling 23 in accordance with the present invention, together with a release tool 24 and, in outline, a pipe 25. The coupling 23 is a simple in-line coupling with connecting portions at each end which internally correspond to that described above, having a pair of interlocking grip rings. As shown, the pipe 25 is held in the coupling but the release tool is in position to be moved axially into the coupling to release the grip on the pipe 25 and permit its withdrawal from the coupling.

The plastics release tool 24, which is also illustrated in Figure 5, is separate from the coupling and only put in position when it is desired to release a pipe. The release tool 24 has been moulded to as to be in two substantially semi-cylindrical portions 26 and 27, hinged at 28 and separated by a gap 29. Flanges 30 and 31 are formed at one end of the portions 26 and 27 to assist in manipulation of the tool. In use, the release tool 24 is opened out, placed over the pipe 25, and then closed up to form a close fit around the pipe.

It can then be urged axially into the coupling.

The free ends of the portions 26 and 27 are chamfered as indicated at 32, so as to form a cam surface to cooperate with the cam surface on the first grip ring within the coupling, which will be equivalent to the cam surface 19 on the grip ring 5 described above. Axial movement of the release tool 24 into the coupling 23 will therefore result in both grip rings releasing from the pipe 25 and permitting removal or adjustment of the pipe. After use, the release tool can be withdrawn from the coupling and removed from the pipe.

Whilst some preferred features of the present invention have been described in detail above it will be appreciated that many variations are possible within the scope of the invention whose several aspects have been set out. The use of two or more, preferably interlocked, grip rings will be advantageous in a wide range of applications.

Claims

CLAIMS 1. A pipe coupling comprising a body defining a pipe receiving bore, a seal within the bore, and a grip ring within the bore, the grip ring being movable axially into engagement with a cooperating surface which compresses the grip ring radially into engagement with a pipe in the bore in use, characterised in that a second, separate grip ring is provided in the bore, the second grip ring being engaged in use with the first grip ring in such a way that engagement of the first grip ring with the cooperating surface also urges the second grip ring into engagement with a pipe in the bore in use.
2. A pipe coupling as claimed in claim 1, characterised in that the first and second grip rings each comprise a plastics body in which are embedded metallic pipe gripping portions.
3. A pipe coupling as claimed in claim 2, characterised in that each plastics body has embedded therein a single ring of metal defining the gripping portions.
4. A pipe coupling as claimed in claim 3, characterised in that each ring of metal defines a plurality of circumferentially spaced teeth which constitute the gripping portions.
5. A pipe coupling as claimed in any preceding claim, characterised in that the first and second grip rings are substantially identical.
6. A pipe coupling as claimed in any preceding claim, characterised in that the two grip rings interlock.
7. A pipe coupling as claimed in claim 6, characterised in that the trailing edge of the first grip ring is provided with a recess which receives the leading edge of the second grip ring.
8. A pipe coupling as claimed in any preceding claim, characterised in that the coupling is provided with an end portion which defines a first cam surface and the first grip ring is provided on its leading edge with a second cam surface for engagement with the first cam surface, such that engagement of the first and second cam surfaces causes the engaging portions of the grip ring to be urged into gripping engagement with the surface of a pipe received in the bore in use; in that the first grip ring is further provided on its leading edge with a third cam surface which is arranged so that it can be engaged by a release tool which is movable axially with respect to a pipe in use so that the pipe engaging portions of the grip ring can be urged away from engagement with the pipe; and in that the first and second grip rings are engaged in such a manner that when the pipe engaging portions of the first grip ring are urged away from engagement with the pipe under the action of the release tool the pipe engaging portions of the second grip ring are similarly urged away from engagement with the pipe.
9. A pipe coupling as claimed in claim 8, characterised in that the second grip ring is provided with cam surfaces on its leading edge corresponding to the second and third cam surfaces of the first grip ring; and in that the trailing edge of the first grip ring is provided with a recess which receives the leading edge of the second grip ring, including the cam surfaces thereon.
10. A pipe coupling as claimed in any preceding claim, characterised in that the first and second grip rings are arranged in such a way as to be capable of relative rotation.
11. A grip ring for use in a pipe coupling, the grip ring having pipe gripping portions and having a leading edge and a trailing edge, the leading edge being provided with a radially outwardly facing, tapering cam surface for engaging a member in the coupling which will compress the grip ring radially inwards to grip a pipe in use, and a radially inwardly facing, tapering cam surface for engaging a release tool which will cause the grip ring to release its grip on a pipe in use, characterised in that the trailing edge of the grip ring is profiled so as to be capable of receiving the leading edge of a like grip ring.
12. A grip ring as claimed in claim 11, characterised in that it comprises a plastics body in which are embedded metallic pipe gripping portions.
13. A grip ring as claimed in claim 11 or 12, characterised in that the trailing edge of the grip ring is provided with a substantially V section groove.
14. A pipe coupling substantially as hereinbefore described with reference to the accompanying drawings.
15. A grip ring for a pipe coupling, substantially as hereinbefore described with reference to the accompanying drawings.
16. A pipe coupling comprising a main body defining a pipe receiving bore, an end member which is attached to one end of the main body and part of which defines a mouth for the bore, a seal within the bore, and an axially movable grip ring within the bore between the seal and the mouth, the grip ring including pipe engaging portions which engage the surface of a pipe received in the bore in use; wherein the end member is provided with a first cam surface and the grip ring is provided on its leading edge with a second cam surface for engagement with the first cam surface, such that engagement of the first and second cam surfaces causes the engaging portions of the grip ring to be urged into gripping engagement with the surface of a pipe received in the bore in use; and wherein the grip ring is further provided on its leading edge with a third cam surface which is arranged so that it can be engaged by a release tool which is movable axially with respect to a pipe in use so that the engaging portions of the grip ring can be urged away from engagement with the pipe; characterised in that a second, like grip ring is provided within the bore, the second grip ring having cam surfaces on its leading edge corresponding to the second and third cam surfaces of the first grip ring, and in that the trailing edge of the first grip ring is provided with a recess which receives the leading edge of the second grip ring, including the cam surfaces thereon.
17. A grip ring for a pipe coupling, comprising a plastics body in which are embedded metallic pipe gripping portions, characterised in that the plastics body is provided at its trailing edge with means for interlocking engagement with the leading edge of a like grip ring when arranged coaxially therewith.
18. A pipe coupling comprising a body defining a pipe receiving bore, a seal within the bore, and a grip ring within the bore, characterised in that a second grip ring is provided within the bore in an interlocked arrangement with the first grip ring.
19. A pipe coupling comprising pipe gripping means which includes at least two coaxially arranged grip rings which have been manufactured separately but have been mechanically interlocked during assembly of the coupling.
20. A pipe coupling comprising pipe gripping means which includes at least two coaxially arranged grip rings which have been manufactured separately but have been joined together, characterised in that each grip ring comprises a plastics body in which are embedded metallic pipe gripping portions.